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Title: Bimetallic and Ternary Alloys for Improved Oxygen Reduction Catalysis

Abstract

Using a combination of density functional theory (DFT) calculations and an array of experimental techniques including in-situ x-ray absorption spectroscopy, we identified, synthesized, and tested successfully a new class of electrocatalysts for the oxygen reduction reaction (ORR) that were based on monolayers of Pt deposited on different late transition metals (Au, Pd, Ir, Rh, or Ru), of which the Pd-supported Pt monolayer had the highest ORR activity. The amount of Pt used was further decreased by replacing part of the Pt monolayer with a third late transition metal (Au, Pd, Ir, Rh, Ru, Re, or Os). Several of these mixed Pt monolayers deposited on Pd single crystal or on carbon-supported Pd nanoparticles exhibited up to a 20-fold increase in ORR activity on a Pt-mass basis when compared with conventional all-Pt electrocatalysts. DFT calculations showed that their superior activity originated from the interaction between the Pt monolayer and the Pd substrate and from a reduced OH coverage on Pt sites, the result of enhanced destabilization of Pt-OH induced by the oxygenated third metal. This new class of electrocatalysts promises to alleviate the major problems of existing fuel cell technology by simultaneously decreasing materials cost and enhancing performance.

Authors:
 [1];  [2];  [3];  [3];  [3];  [3];  [1]
  1. University of Wisconsin, Madison
  2. ORNL
  3. Brookhaven National Laboratory (BNL)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Center for Nanophase Materials Sciences
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
930892
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Topics in Catalysis; Journal Volume: 46; Journal Issue: 3-4
Country of Publication:
United States
Language:
English

Citation Formats

Nilekar, Anand Udaykumar, Xu, Ye, Zhang, Junliang, Vukmirovic, Miomir B., Sasaki, Kotaro, Adzic, Radoslav R., and Mavrikakis, Manos. Bimetallic and Ternary Alloys for Improved Oxygen Reduction Catalysis. United States: N. p., 2007. Web. doi:10.1007/s11244-007-9001-z.
Nilekar, Anand Udaykumar, Xu, Ye, Zhang, Junliang, Vukmirovic, Miomir B., Sasaki, Kotaro, Adzic, Radoslav R., & Mavrikakis, Manos. Bimetallic and Ternary Alloys for Improved Oxygen Reduction Catalysis. United States. doi:10.1007/s11244-007-9001-z.
Nilekar, Anand Udaykumar, Xu, Ye, Zhang, Junliang, Vukmirovic, Miomir B., Sasaki, Kotaro, Adzic, Radoslav R., and Mavrikakis, Manos. Mon . "Bimetallic and Ternary Alloys for Improved Oxygen Reduction Catalysis". United States. doi:10.1007/s11244-007-9001-z.
@article{osti_930892,
title = {Bimetallic and Ternary Alloys for Improved Oxygen Reduction Catalysis},
author = {Nilekar, Anand Udaykumar and Xu, Ye and Zhang, Junliang and Vukmirovic, Miomir B. and Sasaki, Kotaro and Adzic, Radoslav R. and Mavrikakis, Manos},
abstractNote = {Using a combination of density functional theory (DFT) calculations and an array of experimental techniques including in-situ x-ray absorption spectroscopy, we identified, synthesized, and tested successfully a new class of electrocatalysts for the oxygen reduction reaction (ORR) that were based on monolayers of Pt deposited on different late transition metals (Au, Pd, Ir, Rh, or Ru), of which the Pd-supported Pt monolayer had the highest ORR activity. The amount of Pt used was further decreased by replacing part of the Pt monolayer with a third late transition metal (Au, Pd, Ir, Rh, Ru, Re, or Os). Several of these mixed Pt monolayers deposited on Pd single crystal or on carbon-supported Pd nanoparticles exhibited up to a 20-fold increase in ORR activity on a Pt-mass basis when compared with conventional all-Pt electrocatalysts. DFT calculations showed that their superior activity originated from the interaction between the Pt monolayer and the Pd substrate and from a reduced OH coverage on Pt sites, the result of enhanced destabilization of Pt-OH induced by the oxygenated third metal. This new class of electrocatalysts promises to alleviate the major problems of existing fuel cell technology by simultaneously decreasing materials cost and enhancing performance.},
doi = {10.1007/s11244-007-9001-z},
journal = {Topics in Catalysis},
number = 3-4,
volume = 46,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. Using a combination of density functional theory (DFT) calculations and an array of experimental techniques including in situ X-ray absorption spectroscopy, we identified, synthesized, and tested successfully a new class of electrocatalysts for the oxygen reduction reaction (ORR) that were based on monolayers of Pt deposited on different late transition metals (Au, Pd, Ir, Rh, or Ru), of which themore » Pd-supported Pt monolayer had the highest ORR activity. The amount of Pt used was further decreased by replacing part of the Pt monolayer with a third late transition metal (Au, Pd, Ir, Rh, Ru, Re, or Os). Several of these mixed Pt monolayers deposited on Pd single crystal or on carbon-supported Pd nanoparticles exhibited up to a 20-fold increase in ORR activity on a Pt-mass basis when compared with conventional all-Pt electrocatalysts. DFT calculations showed that their superior activity originated from the interaction between the Pt monolayer and the Pd substrate and from a reduced OH coverage on Pt sites, the result of enhanced destabilization of Pt–OH induced by the oxygenated third metal. This new class of electrocatalysts promises to alleviate the major problems of existing fuel cell technology by simultaneously decreasing materials cost and enhancing performance.« less
  • The effect of base metal oxide (nonnoble metal oxide) in a Pt-Cr-Cu alloy catalyst is investigated for the oxygen reduction reaction in a solid-polymer-electrolyte fuel cell. The cathode mass activities at 0.9 V for Pt, Pt-Cr alloy, Pt-Cr-Cu alloy, and a mixture of Pt-Cr-Cu alloy with base metal oxide are compared. The enhancement factor is largest (about 6 times) for the mixture of Pt-Cr-Cu alloy with base metal oxide, compared to Pt-Cr and Pt-Cr-Cu alloys (about 2 times). The higher electrocatalytic activity of this material may be due to the combined effects of the Pt-Cr-Cu alloy and the base metalmore » oxide. The physical and electrochemical characterizations are carried out using various techniques like X-ray diffraction, transmission electron microscopy, cyclic voltammetry, polarization, and ac impedance.« less
  • Here, we present a generic analysis of the implications of energetic scaling relations on the possibilities for bifunctional gains at homogeneous bimetallic alloy catalysts. Such catalysts exhibit a large number of interface sites, where second-order reaction steps can involve intermediates adsorbed at different active sites. Using different types of model reaction schemes, we show that such site-coupling reaction steps can provide bifunctional gains that allow for a bimetallic catalyst composed of two individually poor catalyst materials to approach the activity of the optimal monomaterial catalyst. However, bifunctional gains cannot result in activities higher than the activity peak of the monomaterialmore » volcano curve as long as both sites obey similar scaling relations, as is generally the case for bimetallic catalysts. These scaling-relation-imposed limitations could be overcome by combining different classes of materials such as metals and oxides.« less
  • No abstract prepared.
  • An analysis of X-ray absorption spectroscopy (XAS) data [X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS)] at the Pt L{sub 3} edge for Pt-M bimetallic materials (M=Co, Cr, Ni, Fe) and at the Co K edge for Pt-Co is reported for Pt-M/C electrodes in HClO{sub 4} at different potentials. The XANES data are analyzed using the {Delta}{mu} method, which utilizes the spectrum at some potential V minus that at 0.54 V reversible hydrogen electrode (RHE) representing a reference spectrum. These {Delta}{mu} data provide direct spectroscopic evidence for the inhibition of OH chemisorption on the cluster surfacemore » in the Pt-M. This OH chemisorption, decreasing in the direction Pt>Pt-Ni>Pt-Co>Pt-Fe>Pt-Cr, is directly correlated with the previously reported fuel cell performance (electrocatalytic activities) of these bimetallics, confirming the role of OH poisoning of Pt sites in fuel cells. EXAFS analysis shows that the prepared clusters studied have different morphologies, the Pt-Ni and Pt-Co clusters were more homogeneous with M atoms at the surface, while the Pt-Fe and Pt-Cr clusters had a 'Pt skin.' The cluster morphology determines which previously proposed OH inhibition mechanism dominates, the electronic mechanism in the presence of the Pt skin, or lateral interactions when M-OH groups exist on the surface.« less